London Ambulance Service has admitted a catalogue of errors after a late response to an emergency call left a woman brain damaged.

Caren Paterson collapsed and suffered serious brain injuries after she was forced to wait nearly two hours for an ambulance which was just 100 yards away.

Paramedics had been ordered not to enter her flat without a police escort as officers had previously attended the premises and it was graded as high risk.

The delay caused her brain to be starved of oxygen, leaving her hospital bound and in need of specialist care for the rest of her life.

Lawyers acting on her behalf have demanded urgent improvements in the handling of 999 calls in London after the capital’s ambulance service admitted 11 separate breaches of duty.

Ms Paterson, 33, collapsed in the bedroom of her Islington flat early in the afternoon of October 27, 2007, and her condition quickly deteriorated, prompting her boyfriend to call 999 and report that she was unconscious, breathing abnormally and her lips were blue.

However, because police had previously been called to the Hargrave Road address, it was flagged as being on the High Risk Address Register and the ambulance crew was told to wait for a police escort.

There were no police available at that time and, despite a further two 999 calls from her boyfriend, the emergency medical team waited for over an hour just 100 yards from her flat.

Ms Paterson, who had been working as a researcher at King’s College Hospital, eventually suffered a cardiac arrest at around 3.15pm, five minutes before police and an ambulance team arrived.

She now suffers long-term brain injury symptoms including chronic amnesia, anger outbursts, confusion and disorientation.

Her lawyer, John Davis, said it was not known why her property was on the high-risk register.

He said: “There is a list of failings and breaches of duty that occurred in response to the 999 call.

“It is particularly heartbreaking for Ms Paterson’s family to know that an emergency response team was in very close proximity to her but unable to give her the crucial treatment she needed.

“The emergency crews eventually arrived 102 minutes after the first 999 call - but even then there was nobody senior enough on hand to administer the treatment that Ms Paterson needed.

“It is imperative that people in Ms Paterson’s condition are treated as quickly as possible - even seconds can make a huge difference, let alone over an hour and a half.

“The emergency services had been made abundantly aware of the seriousness of her condition yet failed on several levels to handle the situation in accordance with their own guidelines.

“But for these failings and contraventions, Ms Paterson would have received appropriate medical treatment sooner, would have been taken to A&E sooner, and consequently would not have suffered the injuries she did.

“Following Ms Paterson’s case, it has been acknowledged that the way the High Risk Address Register was operated needed to be radically overhauled - we endorse any review and improvement to this system which was clearly at the heart of the failings in this case.

“We appreciate the London Ambulance Service’s admission of liability for the failings and we will now be working to secure a care package that will allow Ms Paterson to live in as much comfort as possible, and will afford her family some degree of peace of mind.”

Ms Paterson’s mother, Eleanor Paterson, of Warkworth, Northumberland, said: “We welcome the admission of liability as a significant step towards ensuring Caren will continue to receive the care, treatment and specialist attention she will need for the rest of her life, but nothing will return our daughter to the way we knew her.

“The thought of an ambulance crew sitting waiting while my daughter lay in her flat as her condition went from serious to life-threatening, causing irreparable damage to her brain, is still shocking.

“Although I appreciate fully that the emergency services have guidelines in place, I now know that there were further procedures that should have been followed and, if they had been, my daughter would have received the treatment she needed.”

The London Ambulance Service admitted 11 separate breaches of duty that contributed to Ms Paterson’s injuries, including failing to comply with hospital trust policies, failing to recognise there was no danger at the flat, and failing to assess the life threatening nature of Ms Paterson’s injuries.

A London Ambulance Service spokesman said: “We would like again to offer our sincere apologies to Dr Caren Paterson and to her family.

“We carried out a detailed investigation into the circumstances of the incident and we have accepted liability for the shortcomings in the care that was provided on October 27, 2007.

“Dr Paterson is bringing a claim for compensation against the Service and we hope that the legal representatives can now work together to find a resolution.”